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The complexity of human's cooperative behavior cannot be fully explained by theories of kin selection and group selection. If reciprocal altruism is to provide an explanation for altruistic behavior, it would have to depart from direct reciprocity, which requires dyads of individuals to interact repeatedly. For indirect reciprocity to rationalize cooperation among genetically unrelated or even culturally dissimilar individuals, information about the reputation of individuals must be assessed and propagated in a population. Here, we propose a new framework for the evolution of indirect reciprocity by social information: information selectively retrieved from and propagated through dynamically evolving networks of friends and acquaintances. We show that for indirect reciprocity to be evolutionarily stable, the differential probability of trusting and helping a reputable individual over a disreputable individual, at a point in time, must exceed the cost-to-benefit ratio of the altruistic act. In other words, the benefit received by the trustworthy must out-weigh the cost of helping the untrustworthy.  相似文献   

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Increasing numbers of research studies test interventions for clinicians in addition to or instead of interventions for patients. Although previous studies have enumerated barriers to patient enrolment in clinical trials, corresponding barriers have not been identified for enrolling clinicians as subjects. We propose a framework of metrics for evidence-based estimation of time and resources required for recruiting clinicians as research participants, and present an example from a federally funded study. Our framework proposes metrics for tracking five steps in the recruitment process: gaining entry into facilities, obtaining accurate eligibility and contact information, reaching busy clinicians, assessing willingness to participate, and scheduling participants for data collection. We analyzed recruitment records from a qualitative study exploring performance feedback at US Department of Veterans Affairs Medical Centers (VAMCs); five recruiters sought to reach two clinicians at 16 facilities for a one-hour interview. Objective metrics were calculable for all five steps; metric values varied considerably across facilities. Obtaining accurate contact information slowed down recruiting the most. We conclude that successfully recruiting even small numbers of employees requires considerable resourcefulness and more calendar time than anticipated. Our proposed framework provides an empirical basis for estimating research-recruitment timelines, planning subject-recruitment strategies, and assessing the research accessibility of clinical sites.  相似文献   

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Environmental conditions such as housing and husbandry have a major impact on the laboratory animal throughout its life and will thereby influence the outcome of animal experiments. However, housing systems for laboratory animals have often been designed on the basis of economic and ergonomic aspects. One possible way to improve the living conditions of laboratory animals is to provide opportunities for the animals to perform a species-specific behavioral repertoire. Environmental enrichment should be regarded both as an essential component of the overall animal care program and equally important as nutrition and veterinary care. The key component of an enrichment program is the animal staff, whose members must be motivated and educated. It is critically important to evaluate environmental enrichment in terms of the benefit to the animal by assessing the use of and preference for a certain enrichment, the effect on behavior and the performance of species-typical behavior, and the effect on physiological parameters. At the same time, it is necessary to evaluate the impact on scientific outcome, how the enrichment influences the scientific study, and whether and how the statistical power is affected. The result will depend on the parameter measured, the type of enrichment used, and the animal strain. In this article, goals of enrichment are defined and discussed. Animal behaviors and needs are described, along with the translation of those needs into environmental enrichment programs. Specific types of environmental enrichment are outlined with examples from the literature, and an evaluation of environmental enrichment is provided.  相似文献   

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Ionizing radiation poses a significant risk to humans living and working in space. The major sources of radiation are solar disturbances and galactic cosmic rays. The components of this radiation are energetic charged particles, protons, as well as fully ionized nuclei of all elements. The biological effects of these particles cannot be extrapolated in a straightforward manner from available data on x-rays and -rays. A radiation protection program that meets the needs of spacefaring nations must have a solid scientific basis, capable not only of predicting biological effects, but also of making reliable estimates of the uncertainty in these predictions. A strategy leading to such predictions is proposed, and scientific requirements arising from this strategy are discussed.Invited paper presented at the International Symposium on Heavy Ion Research: Space, Radiation Protection and Therapy, Sophia-Antipolis, France, 21–24 March 1994  相似文献   

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Background

The global HIV prevention community is implementing voluntary medical male circumcision (VMMC) programs across eastern and southern Africa, with a goal of reaching 80% coverage in adult males by 2015. Successful implementation will depend on the accessibility of commodities essential for VMMC programming and the appropriate allocation of resources to support the VMMC supply chain. For this, the United States President’s Emergency Plan for AIDS Relief, in collaboration with the World Health Organization and the Joint United Nations Programme on HIV/AIDS, has developed a standard list of commodities for VMMC programs.

Methods and Findings

This list of commodities was used to inform program planning for a 1-y program to circumcise 152,000 adult men in Swaziland. During this process, additional key commodities were identified, expanding the standard list to include commodities for waste management, HIV counseling and testing, and the treatment of sexually transmitted infections.The approximate costs for the procurement of commodities, management of a supply chain, and waste disposal, were determined for the VMMC program in Swaziland using current market prices of goods and services.Previous costing studies of VMMC programs did not capture supply chain costs, nor the full range of commodities needed for VMMC program implementation or waste management. Our calculations indicate that depending upon the volume of services provided, supply chain and waste management, including commodities and associated labor, contribute between US$58.92 and US$73.57 to the cost of performing one adult male circumcision in Swaziland.

Conclusions

Experience with the VMMC program in Swaziland indicates that supply chain and waste management add approximately US$60 per circumcision, nearly doubling the total per procedure cost estimated previously; these additional costs are used to inform the estimate of per procedure costs modeled by Njeuhmeli et al. in “Voluntary Medical Male Circumcision: Modeling the Impact and Cost of Expanding Male Circumcision for HIV Prevention in Eastern and Southern Africa.” Program planners and policy makers should consider the significant contribution of supply chain and waste management to VMMC program costs as they determine future resource needs for VMMC programs. Please see later in the article for the Editors'' Summary  相似文献   

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Due to conservation needs, reliable rapid-assessment methods for mapping of biodiversity are needed. One approach is to use surrogates, i.e. quantities that correlate strongly with the number of species, but are easier to obtain. The purpose of this paper is to test two polychaete surrogates, one for higher taxa and one for indicator groups, that will facilitate prediction of species richness in marine soft-bottom communities. Soft sediment is an important habitat which covers most of the ocean bottom. Data on polychaetes from the North Atlantic were used since polychaetes are often numerically dominant in the benthic assemblages, both with regard to the number of species and their abundance. In the polychaete assemblages along the Norwegian coast, richness at the genus, family and order level were significantly, linearly correlated to total species richness (r 0.92). Polychaetes in the order Terebellida were found to be a good indicator of polychaete species richness and to a lesser extent also of whole benthic assemblages. The group Terebellida is potentially well suited as an indicator group, since it contains long-lived, large species that are easy to sort from the sediment and it is well defined taxonomically. Although promising as proxies for species richness in marine biodiversity studies, the use of lower taxonomic resolution and indicator groups requires further investigations in more local areas where there are conservation issues.  相似文献   

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Human research in delay discounting has omitted several procedures typical of animal studies: forced-choice trials, consequences following each response, and assessment of stable response patterns. The present study manipulated these procedures across two conditions in which real or hypothetical rewards were arranged. Six college students participated in daily sessions, in which steady-state discounting of hypothetical and real rewards was assessed. No systematic effects of repeated exposure to hypothetical rewards was detected when compared with first day assessments of discounting. Likewise, no systematic effect of reward type (real versus hypothetical) was detected. When combined with previous research failing to detect a difference between hypothetical and potentially real rewards, these findings suggest that assessing discounting of hypothetical rewards in single sessions is a practical and valid procedure in the study of delay discounting.  相似文献   

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Forests provide 1.75 billion cubic meters of timber each year and a similar amount of fuel wood. Our understanding of forest ecosystems is far from complete. Biotechnology can provide means to speed up adaptation by forest species in response to pathogen introduction, climate change, or other perturbations. Consensus building on forest issues is always likely to be difficult, as diversity in the nature of forests and their cultural and historical significance must be recognized. The potential risks and possible benefits of deploying or choosing not to deploy forest biotechnology products must be considered on a case-by-case, product- rather than process-driven basis for rational, evidence-based decisions to be reached. Aspects of ecologically neutral field trials, ecological and social perceptions of risk, and steady state and dynamic paradigms of nature are discussed alongside challenges facing biotechnology in adequately avoiding or limiting risks to allow deployment in forests. Communicated by Ronald Sederoff  相似文献   

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Just like you would not buy a car without key information such as service history, you would not "buy" a clinical trial report without key information such as concealment of allocation. Implementation of the updated CONSORT 2010 statement enables the reader to see exactly what was done in a trial, to whom and when. A fully "CONSORTed" trial report does not necessarily mean the trial is a good one, but at least the reader can make a judgement. Clear reporting is a pre-requisite for judgement of study quality. The CONSORT statement evolves as empirical research moves on. CONSORT 2010 is even clearer than before and includes some new items with a particular emphasis on selective reporting of outcomes. The challenge is for everyone to use it.  相似文献   

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In captivity, male bonnet macaques (Macaca radiata) frequently express "friendship" toward one another, including affiliative behavior such as huddling, grooming, coalitionary support, and sitting in close proximity. The purpose of this study was to determine whether wild adult male bonnet macaques also express "friendship" by investigating whether or not (1) adult male bonnet macaques have affiliative social relationships with other males, (2) the strength of social relationships varies among dyads, (3) there is time-matched reciprocity in allogrooming among dyads, and if so, whether the level of reciprocity occurs within a bout of grooming, a day, or over 2 months (the limit of this study), and (4) a correlation exists between the strength of social relationships and dominance ranks among adult males. Focal samples totaling 150 hr on all seven adult males in one study group were conducted to record both agonistic and affiliative interactions. Agonistic interactions were used to construct a dominance hierarchy, whereas affiliative interactions (sitting in proximity to within 1 m with and without grooming) were used to quantify the existence and strength of social bonds within dyads. Results show that adult male bonnet macaques had differentiated affiliative relationships with other males in their group. There was little reciprocity of grooming within a bout of grooming or within a day, but greater reciprocity over the study period of 2 months. There was no correlation between dominance ranking distance and the strength of affiliative relationship within dyads; however, within dyads lower-ranking males groomed higher-ranking males more than vice versa. This study suggests that friendships in male bonnet macaques are characterized not by immediate tit-for-tat reciprocal altruism, but by reciprocity over a longer time span, and that affiliative social relationships may be less constrained by agonistic relationships than is the case in more despotic species of macaques.  相似文献   

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Abstract   Apart from flies, ants are Australia's most noticeable and studied insects. In addition to their sheer abundance and ubiquity in most terrestrial ecosystems, they are also exceptionally diverse. Here, we outline the history of describing the Australian ant fauna and document the resources that are available for identifying and researching them. Unusual patterns in chromosome numbers in individual species are discussed, and the rediscovery of an ancient ant is described. A framework for understanding the dynamics of Australian ant communities is outlined, and the functional groups that fall within this framework are documented. The predictability of responses of ant communities to stress and disturbance has enabled a protocol for using ants as bioindicators of environmental health and integrity to be developed. This has been exported and adapted to other regions of the world. Australian ant research has also lead to promising sources of biopharmaceuticals. As well as describing these two practical applications of Australian ant research, this review looks at some of the future directions that studies on Australian ants might take.  相似文献   

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